1. Field of the Invention
This invention relates to the field of power transmission gearboxes for use in irrigation equipment, and more particularly to a drive line protection system to shield the irrigation drive train extending from said gearboxes.
2. Description of the Prior Art
Center pivot and linear irrigation systems are becoming increasingly popular to irrigate large sections of land. Typically, such systems are capable of watering a quarter section of land, i.e., 160 acres, or more. A center pivot irrigation system generally comprises an elongated primary irrigation pipe that extends radially outward from a center pivot. When activated, the irrigation pipe rotates around the pivot, thereby watering the area that the irrigation system passes over and resulting in a circular pattern of water coverage about the central pivot point. The length of time involved in a 360 degree rotation of the irrigation pipe may be up to several days. Likewise, linear systems are comprised of similar irrigation pipes, but move linearly across sections of land to be irrigated.
In conventional irrigation systems, the elongated irrigation pipe or span is supported at spaced apart intervals by a plurality of wheeled towers. Extending between each set of adjacent towers is a truss arrangement utilized to support the span and the water deployment system. Sprinklers are located at spaced intervals along the length of the span or a parallel water conduit. The wheels of each tower are normally positioned perpendicular to the span to permit the tower to follow a prescribed path, either circular for center pivot systems or linear for linear systems. Each tower is typically provided with one or more drive motors operable to move the tower in synchronization with the other towers such that the overall length of the span is maintained in substantially a straight line as the irrigation system moves through its prescribed path. In most conventional systems, the drive motors are either electric or hydraulic and referred to as center drive or drive gear motors. In systems using electric motors, each drive motor is typically located midway between the wheels on which the tower is supported. Each wheel is connected to a wheel drive gearbox. To transfer power to each wheel, a drive shaft extends outwardly, substantially parallel with the ground, from the center drive motor to each wheel drive where the drive shaft engages the wheel drive. Typically, the gear shaft will extend through the gearbox and protrude from the opposite side of the gearbox. Since such irrigation systems may take several days to complete a single watering cycle rotation, the output revolutions per minute of the center drive motors and drive shafts are very low, generally in the range of 28-86 rpm depending on the center drive type.
One drawback to the above-described prior art arrangement is that rotating elements of the drive train, such as the drive shafts, are either exposed or covered with a rigid conduit that rotates along with the drive shaft, in each instance creating safety concerns for those persons in proximity to the rotating elements. Another drawback with such systems is that the drive trains are exposed to the environment. Drive trains exposed to agricultural environments may be subject to hazards such as moisture, dirt, insects and temperature extremes, all of which could damage the integrity of the irrigation systems, and in particular, the drive trains of such systems. Particularly vulnerable areas on wheel drives and drive gear motors are the seals adjacent the point where the drive shaft extends from the gearbox. Should the seals become compromised in any way, center drive or wheel drive lubricant could leak from the gearbox resulting in failure of the drive train. One solution has been to loosely place rigid conduit over the drive shaft. Specifically, a plastic conduit having a diameter only slightly larger than the drive shaft is fitted around the drive shaft. An endbell may also be clamped to the conduit to cover larger connecting linkages. In any event, such prior art shields spin freely on the drive shaft or rotate in conjunction with the drive shaft, doing little to protect the drive trains at the open ends of the conduit, especially the gearbox seals. Nor does such a system eliminate the above mentioned safety concerns for persons in proximity to the rotating drive shaft. In fact, use of such conduit results in new drawbacks, since the ends of the conduit adjacent the gearbox tend to wear grooves in the gearbox housing potentially resulting in leakage of gearbox lubricants and exposing the gears to particulate debris that can damage the gearbox.
Still yet another agricultural problem characteristic of such exposed drive shafts is "crop wrap" wherein crops, vegetation and other debris tend to become entwined on or otherwise attached to the rotating elements of the drive train, including the drive shaft, the coupler connecting the drive shaft to input shaft of the wheel drives, and the output shaft of the drive gear motor. The low rpms of the drive train further exacerbate the problem since such debris is more likely to become entwined on slower turning components. Debris wound around the drive train can damage both the seals and the turning components, inhibiting operation of the irrigation system and potentially resulting in gearbox and gear motor failure. In many instances, the irrigation systems are simply placed into service and not routinely examined or checked. As a result, the only time an operator becomes aware of a problem with the irrigation system is after the system has already failed. One solution to crop wrap has been to simply assign personnel to travel out to the irrigation site to periodically remove such debris. However the need to remove such debris may occur as many as several times a day. In that such irrigation systems are otherwise automated and located in remote areas, such a solution is time consuming and expensive. In addition, since the system must be shut down to safely remove such debris, there is a down time associated with such a procedure. Furthermore, use of the prior art shield described above is ineffective since the rotating ends of the drive train remain exposed, permitting debris to migrate into both the shield and the gearboxes.
Notwithstanding these drawbacks, many such irrigation systems are now used on uneven ground, for example, hills or in valleys, where an exposed drive shaft could more easily come into contact with the ground or low growing vegetation resulting in the above described problems. Another problem often encountered in use of irrigation systems is that the wheels of the irrigation systems tend to form ruts or tracks which can extend a considerable depth into the ground, making it more likely that a drive shaft attached to such wheel will be exposed to dirt, vegetation or other debris that could damage the rotating members of the drive train, as well as gearbox and gear motor seals, resulting in interruption of the operation of the irrigation system.